package day7;

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import java.util.TreeMap;

public class TestMap {
    public static void main(String[] args) {
        Map<String,Integer> map = new HashMap<>();
        //不允许key和value为空
        //默认11 0.75 2n+1
        //线程安全(方法添加了同步锁) 效率比较低
        Map<String,Integer> map2 = new Hashtable<>();
        map.put(null,100);
        map.put("java",null);
        map.put(null,null);
        System.out.println(map);
        Map<String,Integer> map3 = new TreeMap<>();
    }
}
